I think what you're trying to do is use the functionallity of 'tail -f file' in perl. For that, I usually use seek. Here's a snipplet of how to use it:

open (FILE,"newfile") or die "Can't read file: $!";
my $continue = 1;

while ($continue) {
  while (<FILE>) {
    # do something with $_
    if (/some_end_condition/) {
      $continue = 0;
      last;
    }
  }
  # when we get here, we're at the EOF
  seek (FILE, 0, 1);  # reset the EOF flag
  sleep 1; # wait a bit
}
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-- Dan